A present invention relates to a device for processing sheet material with a colored pattern, based on information of the colored pattern detected from the sheet material.
Heretofore, devices for processing sheet materials with colored patterns have been well known as sewing machines with a pattern matching function (pattern matching sewing machines) which have color sensors.
Many pattern matching sewing machines are known as disclosed in Japanese Laid-Open Patent Publication No. 60-153896, for example. Generally, the known pattern matching sewing machine is provided with color sensors. The pattern matching sewing machine operates to detect, with the color sensors, colored patterns of two fabrics before they are sewn to thereby produce three primary color component signals of red (R), green (G), and blue (B) for the colored patterns of both the two fabrics, calculates a shift (mismatch) amount between the patterns of the two fabrics based on the obtained three primary color component signals for the two fabrics, and adjusting relative feed rates of the fabrics until the patterns of the fabrics match each other.
In order to determine a slight shift amount of the patterns based on the color component signals from the color sensors and attain a highly accurate pattern matching operation, it is necessary that the levels of the three primary color component signals of red (R), green (G), and blue (B) be properly balanced with one another. For example, the three primary color component signals obtained for white color should have their levels equal to one another. In other words, a so-called white balance should be properly adjusted for the color sensors provided in the pattern matching sewing machine.
However, there may occur a problem that the white balance of the color sensors fails to be properly adjusted, due to manufacturing tolerances of the color sensors or aging or environments of use of the sewing machine.